Carbon fiber materials are used to manufacture many parts of bicycles because their high reinforcement, rigidity and light weight. The carbon fiber materials have been promoted to bicycle markets through following four steps:
1. To front fork and rear stays, wherein a requirement of a support force of the front fork and the rear stays focuses on light weight in this step. The manufacturers therefore focus on producing light-weight front fork and rear stays.
2. To crank, seat post and handle bar, wherein a high support force of the crank, the seat post and the handle bar is indispensable for bicycles in this step. Accordingly, manufacturers develop related technologies to produce high rigid crank, seat post and handle bar.
3. To frame, wherein customers require the fame with aesthetics appearance, so manufactures develop good-looking frame at this stage.
4. To rim, wherein a bicycle made of carbon fiber materials are popular at this stage, so manufacturers research and develop related parts of a bicycle made of carbon fiber materials, such as carbon fiber rim.
However, such a carbon fiber rim rubs with brake blocks of a wheel directly during riding bicycle, thus damaging the carbon fiber rim easily.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.